Dunlin

Calidris alpina

By Andy McCormick

Length 8.5 in

Wingspan 17 in

Weight 2.1 oz (60 g)

AOU Band code DUNL

Dunlins are hardy birds that winter farther north than any other shorebird. This fall and winter they will be along the Washington coast from late October to early May. Major stopover points for them are the tidal flats and coastal estuaries around Willapa Bay and Grays Harbor and the Samish and Skagit Flats where they forage on marine and freshwater invertebrates by probing a few centimeters into the mud or fine-grained sand. They can also be found on interior seasonal wetlands. About a half million of them migrate along the Pacific coast each year (Warnock et al).

Dunlins belong to the genus Calidris from the Greek kalidris used by Aristotle to describe a speckled waterbird. Alpina refers to the mountains probably to indicate that Dunlins breed in a cold region of the world. The common name is from the Anglo-Saxon dunn, for dark brown, which is descriptive of their brown back in the basic plumage. The breeding or alternative plumage is quite dramatic with its conspicuous black belly patch and rufous back, giving the bird its old name of Red-backed Sandpiper. The black bill is sturdy with a distinctive downward turn at the tip and its legs are black. When feeding, Dunlins look a little hunchbacked.

Dunlins are most often seen in large, tight, well-coordinated flocks with all of the birds seeming to turn in unison. Recent research analyzing movies of flocks frame by frame are able “to show that a turn ripples through a flock just as a cheerleading wave passes through sports fans at a stadium” (Freiderici). Researchers now think that birds need time to learn this behavior and juveniles who cannot keep up with the flock are often the birds that become isolated and prey for falcons. Both the Merlin and Peregrine Falcon have a hunting style characterized by flying directly into the Dunlin flock to split it in order to separate a single individual for attack. During these attacks the flock can stay together but change shape or it can split into two groups leaving some individuals vulnerable.

In May Dunlins begin the northward migration and return to their breeding grounds in the subarctic and arctic tundra. They nest in a shallow scrape in the gravel and typically four olive to blue-green eggs are deposited. Both parents (female at night and male during the day) incubate the eggs for about three weeks. The female departs the nest a few days after the young hatch. The young then feed themselves and are ready to fly in about a month (Kaufman).

Dunlins are one of the world’s most cosmopolitan shorebirds and are found throughout the year. They were hunted to near extinction in the 1800s. Because they fly so tightly together they are vulnerable to multiple kills with one shotgun blast. They are now protected by the Migratory Bird Treaty Act of 1918 and with assistance from wetland conservation measures their numbers have rebounded. Regrettably Dunlin population declines have recently been recorded in central North America. This is most likely in response to the loss of wintering habitat in the United States.

Photo by Mick Thompson

Rock Sandpiper

Calidris ptilocnemis

By Andy McCormick

Length 9 in

Wingspan 17 in

Weight 2.5 oz

AOU Band code ROSA

The Rock Sandpiper is one of Washington’s wintering shorebirds. It is seen with some regularity along the jetties at Westport and Brown’s Point in Ocean Shores, most often in the company of Surfbirds, Ruddy Turnstones and Black Turnstones, which also forage on rocky shores. It arrives in October and is active through the winter specializing in the splash zone of algae-covered intertidal habitat. It is thought that they will forage more at low tide even during nocturnal low tides (Gil, et al).

They are very similar to and could be considered a western counterpart of the eastern Purple Sandpiper, which also spends much of its time on rocky shores (Alderfer). The Rock Sandpiper winters farther north than any other shorebird with most birds wintering around Cook’s Inlet in Alaska. However, some migrate regularly as far south as northern California.

The Rock Sandpiper is one of the “rockpipers” and is found almost exclusively along rocky shores. It is a member of the large Calidris genus, from the Greek kalidris, used by Aristotle for a speckled waterbird. Its species name ptilocnemis is from the Greek ptilon, a feather, and knemides, armor worn over the shins, referring to soft feathers over the upper part of the leg. This feathering cannot be seen well in the field, and this information is not helpful as a field mark for identification.

Much more helpful for identification in Washington is the bird’s size, which is similar to a Dunlin, and its location on rocks near waves. During breeding season in Alaska, some care must be used regarding location, because some subspecies of Rock Sandpiper will forage on tidal flats. The bird can be separated from the Surfbird by its longer and more drooping bill and the lack of the Surfbird’s white rump (Alderfer).

Rock Sandpipers breed in mossy tundra close to the Yukon River Delta at the Bering Sea and along the Aleutian Islands (Gil, et al). The nest is often on a raised area of moss or grass. A scrape is made by the male and the female deposits four olive- to buff-colored eggs which have brown blotches. Both parents incubate the eggs for about 20 days, but after hatching they are cared for only by the male. Hatchlings leave the nest in about three days and forage for their own food. There is not enough data to know when first flight occurs with any accuracy. In general, Rock Sandpipers eat crustaceans, mollusks, marine worms and unlike most other sandpipers, some plant material such as algae, moss, berries and seeds.

The world population of Rock Sandpipers is around 100,000 individuals. The population has been declining since the 1970s (Kaufman). It is considered a Watch List bird of the Highest Concern (Lebbin, et al). The concern is related to its restricted breeding range and potential adverse effects to its limited wintering sites.

Photo by Mick Thompson

Semipalmated Plover

Charadrius semipalmatus

By Andy McCormick

Length 7.25 in

Wingspan 19 in

Weight 1.6 oz (45 g)

AOU Band code SEPL

The Semipalmated Plover is one of the most common plovers in North America and will attract attention in a flock of shorebirds when it repeatedly runs and stops while foraging for marine worms, crustaceans and small mollusks (Kaufman). It takes a particular stance when stopped. Paulson describes its “’foot-stir,’ with one foot extended forward at about 45 degrees and vibrated on the substrate, presumably causing some invertebrates in their visual field to move and be detected.” The Semipalmated is most often seen along Washington’s coast during spring and fall migration but some have bred in the state.

Along with other North American ringed plovers: Common Ringed, Snowy, Wilson’s, Piping and Mountain Plovers and the Killdeer, the Semipalmated Plover is included in the genus Charadius from the Greek kharadra, ravine or cleft, where some shorebirds may have lived. Most of these birds have a white neck collar and one or two dark breast bands, some of which are partial bands. Both the Semipalmated and its Eurasian relative the Common Ringed Plover (C. hiaticula) have two partially webbed toes which gives our species its name semipalmatus, half palmed, from Latin semi, half and palma, the palm (Holloway).

The Semipalmated Plover is a small, stout bird with a rounded head and no neck. It is medium, dark brown on the head and back with black crown bar and facial markings. A white collar extends around the neck and there is a single black breast band. The eye is dark and set off by a narrow yellow eye ring. The legs are orange and the bill is black with an orange base. It is nearly identical to the Common Ringed Plover and some research indicates they may be one species (Nol & Blanken). The Common Ringed would be rarely seen in Washington. The Wilson’s Plover has pale legs, and the Snowy and Piping Plovers are much paler on the head and back. Simply put in the Pacific Northwest, “A small brown plover with a single breast band will be this species” (Paulson).

In spring this plover migrates from mid April to mid May and nests in the sub-arctic along sand dunes and sandy and gravel shorelines. The nest is a scrape in the gravel sometimes lined with leaves. Generally four olive-buff to olive-brown eggs blotched with black or brown are deposited. Both parents incubate for about 24 days and both feed the young. First flight occurs in another 3-4 weeks (Kaufman). Fall migration is heaviest in August but it can be seen into September. It winters along the Atlantic and Pacific coasts of North, Central and South America. It is one of our birds with the longest migration route.

The Semipalmated is a strong and fast flyer and has been timed at 52km/hr (34mph). It also displays using a butterfly-type flight around the nesting area. Its call is a distinctive, upslurred chu-weet, with the second syllable higher pitched and emphatic (Alderfer).